/***************************************************************************************
* Copyright (c) 2014-2022 Zihao Yu, Nanjing University
*
* NEMU is licensed under Mulan PSL v2.
* You can use this software according to the terms and conditions of the Mulan PSL v2.
* You may obtain a copy of Mulan PSL v2 at:
*          http://license.coscl.org.cn/MulanPSL2
*
* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
* EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
* MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
*
* See the Mulan PSL v2 for more details.
***************************************************************************************/

#include <device/map.h>
#include <device/alarm.h>
#include <utils.h>

static uint32_t *rtc_port_base = NULL;

static void rtc_io_handler(uint32_t offset, int len, bool is_write) {
    assert(offset == 0 || offset == 4);
    /**
    * 获取一次时间会触发两次这个回调函数 rtc_io_handler, 
    * 为避免读一次时间 NEMU 两次调用 get_time(), 需保证 "先读高位寄存器, 再读低位寄存器".
    * 先读高位寄存器, NEMU 会调用 get_time() 更新 rtc 相关寄存器;
    * 再读低位寄存器, NEMU 不会调用再 get_time() 更新 rtc 相关寄存器, 从而读到正确的时间.
    */
    if (!is_write && offset == 4) {
        uint64_t us = get_time();
        rtc_port_base[0] = (uint32_t)us;
        rtc_port_base[1] = us >> 32;
    }
}

#ifndef CONFIG_TARGET_AM
static void timer_intr() {
    if (nemu_state.state == NEMU_RUNNING) {
        extern void dev_raise_intr();
        dev_raise_intr();
    }
}
#endif

void init_timer() {
    rtc_port_base = (uint32_t *)new_space(8);
#ifdef CONFIG_HAS_PORT_IO
    add_pio_map ("rtc", CONFIG_RTC_PORT, rtc_port_base, 8, rtc_io_handler);
#else
    add_mmio_map("rtc", CONFIG_RTC_MMIO, rtc_port_base, 8, rtc_io_handler);
#endif
    IFNDEF(CONFIG_TARGET_AM, add_alarm_handle(timer_intr));
}
